Disclosed herein are a system, apparatus and method for recapturing energy in lift systems.
Many lift systems produce a substantial amount of non-useful energy. These lift systems can be of various configurations such as of a reciprocating type. More particularly, in the case of certain reciprocating lift systems, these reciprocating loads/actions are performed by reciprocating rod-type lift systems. When these lift system produce a substantial amount of non-useful energy it can be dissipated, for example, in the form of heat due to a great extent to the pressure differential of certain fluid regulating devices. This lifting equipment typically has, for instance, elements that move up and/or move down, or which speed up and/or slowdown.
For example, a reciprocating rod lift system can be provided for artificially lifting of down well fluid production systems from a subterranean reservoir or stratus layer(s) for purposes of raising or lowering same to desired positions, and for speeding up or slowing down same. In these systems, much of the total energy used to lift fluid and gas from the well is directed toward operating a sucker rod string and down hole pump.
There is some useful, non-recoverable energy expended in the pumping process, consisting of friction from pivot bearings, mechanical non-continuously lubricated bearings, cables/sheaves, gear box friction, and gear contact friction. In some conventional systems, high pressure nitrogen gas leakage along with heat of compression of said gas results in loss of non-recoverable energy required to counterbalance the weight of the down hole component while lowering the sucker rod string into the well. Still other energy loss occurs for certain non-recoverable inefficiencies such as friction or windage.
Some conventional lift systems provide for a means of recapturing energy by means of storing energy in a physical counterweight or flywheel during a downward stroke of the down hole component. A large mechanical crank mounted counterbalance is used to counter the effect of the down hole component weight and provide resistance to movement as the down hole component is lowered into the well.
Other systems store energy by compressing a gas, such as nitrogen, during the downward stroke. These systems similarly oppose movement of the down hole component and store the energy while lowering the load. A minimum and maximum pressure level is fluctuated based upon an initial precharge ambient temperature and a rate of pressure change.
In yet other conventional lift systems, the fluid flow is restricted over a metering or throttling valve, thereby wasting all the energy contained in the elevation by merely heating the hydraulic fluid. Heat from these throttling devices must then be dispelled employing coolers that use even more energy.
The inherent inefficiencies of these and other conventional systems, in addition to the other non-recoverable energy expended during operation of down well fluid production systems, increase the cost of materials extraction.
The present invention addresses these and other problems associated with the prior art.